The Laboratory Animal Health Facility (LAHF) supports an ever-increasing demand for the use of animals in the Fox Chase Cancer Center's (FCCC) Laboratory Animal Facility (LAF). In 2003, the LAHF supported 46 investigators in all 11 research Programs from all three Divisions at the Center. The vast majority (96%) of use was for peer-reviewed, funded research. The increase in mouse usage during the past five years was 116%, and the use of rodents is anticipated to expand approximately 100% in the next five years. Even as importation of mice from collaborators has increased by over 50% in the past five years, the Facility has maintained and improved the health of the colony. All new strains imported from other Facilities are held in quarantine and monitored for murine disease by serology and polymerase chain reaction (PCR) techniques;most have to be rederived by germ-free cesarean or embryo transfer and raised on disease-free foster mothers in microisolator units before permitted into the main research Facility. Over 81 such cesarean rederivations were done in 2003. The health of animals and their freedom from murine pathogens is constantly monitored by sentinel animals in each animal room, and the entire research Facility has remained viral antibody-free since 1998, Severe immune-deficient mice are bred and successfully live up to two years in the FCCC research colony. Pneumocystis, Pasteurella and Helicobacter have already been eliminated from all breeding and immunodeficient rodent areas, and continued systematic rederivation combined with increased microisolator housing is expected to completely eliminate these agents from all FCCC colonies within two years. In 2003, the LAHF performed 11,967 tests (5,600 microbiological cultures, 3,179 ELISA assays, 2,088 (PCR) assays, and 1,100 necropsies and the number of service hours of direct support to research investigators has increased 210% (1,912 in 2003). Technical support includes animal surgery, antibody production in rabbits, mice and rats, collecting samples from animals, tumor line maintenance, necropsies, tumor and cell culture screening, and microbiological/serological testing. The need for technical services has increased almost four-fold from 1998 (616 service hours) to 2003 (1,912 service hours). This increase is expected to continue parallel to the increase in animal numbers, and an increase of one FTE is projected.